Implementations of trench-gate type devices (e.g., planar-gate metal-oxide-semiconductor field effect transistor (MOSFET) transistors, vertical gate MOSFET transistors, insulated-gate bipolar transistors (IGBTs), rectifiers, and synchronous rectifiers) can include an array of trenches (e.g., parallel trenches) formed in the top surface of the semiconductor die, with each trench filled with a dielectric, a shield electrode and/or a gate electrode, depending upon the type of power device. The trenches can define a corresponding array of mesas (or mesa regions), where each mesa being disposed between adjacent trenches. Depending upon the device implemented on the die, various electrodes and/or doped regions are disposed at the top of the mesa. One or more of the mesas and adjacent trenches can implement a small instance of the device, and the small instances can be coupled together in parallel to provide the whole power semiconductor device. The device can have an ON state where a desired current flows through the device, an OFF state where current flow is substantially blocked in the device, and a breakdown state where an undesired current flows due to an excess off-state voltage being applied between the current conducting electrodes of the device. The voltage at which breakdown is initiated is called the breakdown voltage. Each mesa and adjacent trenches are configured to provide a desired set of ON-state characteristics and breakdown voltage. The configuration of the mesa and trenches can result in a variety of trade-offs between achieving desirable ON-state characteristics, relatively high breakdown voltage, and desirable switching characteristics.
A power semiconductor die can have an active area where the array of mesas and trenches that implement the device are located, a field termination area around the active area, and an inactive area where interconnects and channel stops may be provided. The field termination area can be used to minimize the electric fields around the active area, and may not be configured to conduct current. The breakdown voltage of the device can be determined by the breakdown processes associated with the active area. However, various breakdown processes in the field termination area and inactive area at significantly lower voltages can occur in an undesirable fashion. These breakdown processes may be referred to as passive breakdown processes or as parasitic breakdown processes.
Known field termination areas that have higher breakdown voltages than the active area have been configured, however such known configurations often compromise total die area, processing costs, performance characteristics, and/or so forth. Thus, a need exists for systems, methods, and apparatus to address the shortfalls of present technology and to provide other new and innovative features.